My sister finally got her interview of her visa but she accidentally spoke about her ex fiancé. For the F2B I read that it was for unmarried children over the age of 21 with parents who are green card holders. My sister never married her fiancé so I do not see why she would be denied. On return form it was crossed off for Fraud or misrepresentation and A waiver may be available, please contact USCIS.

If she's not married it doesn't matter. Are you saying they denied her due to misrepresentation? Need to clarify on what exactly that misrepresentation is.

She's not married, so her status remains the same.